Answer : 7 feet
In triangle NQL, point S is the centroid, NS = (x + 10) feet, and SR = (x + 3) feet.
the diagram is attached below
Centroid divides the angle bisector into parts
NS = 2/3 of NR and SR = 1/3 of NR
So NS is 2 times of SR
NS = 2 SR
NS = (x + 10) feet, and SR = (x + 3) feet.
(x+10) =2 (x+3)
x + 10 = 2x + 6 ( subtract 2x and 10 on both sides)
-x = -4
So x=4
SR = x + 3 = 4 + 3 = 7
SR = 7 feet